1. Field of the Invention
The present invention is related to a CDMA portable telephone apparatus, and more specifically, directed to a CDMA portable telephone apparatus for performing a selection operation of a base station.
2. Description of the Related Art
CDMA portable telephone systems, namely portable telephone systems employed in IS-95 (TIA) of USA, and portable telephone systems (will be abbreviated as a “CdmaOne portable telephone system” herein after) employed in T-53 (ARIB) in Japan are described in “standard specification of CDMA type portable automobile telephone system (ARIB STD-T53)” issued from Japanese Denpa Sangyo Kai (ARIB).
Referring now to FIG. 13 to FIG. 23, a description is made of a selection operation of a base station communicated in the case that a portable telephone (will be referred to as a “mobile station” hereinafter) of a CdmaOne portable telephone system issues a telephone call, or receives a telephone call. FIG. 13 is a block diagram for indicating a conventional arrangement of the CdmaOne portable telephone system, and FIG. 14 is a block diagram for representing an arrangement of a base station. FIG. 15 is a block diagram for showing an arrangement of the base station. FIG. 16 is an explanatory diagram for explaining a Walsh code used in the CdmaOne portable telephone system, FIG. 17 is an explanatory diagram for explaining a short PN (Pseudorandom Noise) code used in the CdmaOne portable telephone system, and FIG. 18 is an explanatory diagram for explaining a long PN code used in the CdmaOne portable telephone system. FIG. 19 is an explanatory diagram for explaining use conditions of the Walsh code, the short PN code, and the long PN code in the CdmaOne portable telephone system. FIG. 20 is a flow chart for briefly explaining operations of the mobile station when a base station pilot channel is selected. FIG. 21 is a flow chart for describing detailed operations of the mobile station when the base station pilot channel is selected. FIG. 23 is an explanatory diagram for explaining operation routes of the detailed flow charts indicated in FIG. 21 and FIG. 22.
In FIG. 13, a CdmaOone portable telephone system 300 is arranged by employing a mobile station 301, a first base station 310, a first area 311, a second base station 320, a second area 321, a third base station 330, a third area 331, a switching station 340, an exchanging (repeating) station 350, a first telephone 361, a second telephone 362, and a third telephone 363. The mobile station 301 is located within the first area 311 where the mobile station 301 is communicatable with the first base station 310. As an area located adjacent to the first area 311 of the first base station 310, both the second area 321 and the third area 331 are located. The second base station 320 is present within the second area 321, and the third base station 330 is present within the third base area 331.
The first base station 310, the second base station 320, and the third base station 330 are connected to the switching station 340 via a communication line. The switching station 340 is connected to the exchanging station 350 corresponding to an exchanging station of a wired telephone. The exchanging station 350 is connected via a wired telephone line to the first telephone 361, the second telephone 362, and the third telephone 363, which are owned by subscribers of wired telephones. In an actual case, many other telephones are connected to the exchanging station 350, whereas many other adjacent areas and many other base stations are located in the first area 311, and constitute a peripheral area group and a peripheral base station group, respectively. Outside these peripheral area group and peripheral base station group, communication area groups and communication base station groups are furthermore located. These base stations are also connected to the switching station 340. Also, a large number of mobile stations are located in addition to the mobile station 301 in each of these areas.
FIG. 14 is a block diagram for indicating an arrangement of the first base station 310 shown in FIG. 13.
The first base station 310 is provided with a pilot channel signal generating unit 11, a sink channel signal generating unit 12, a Walsh code modulating unit 13, a paging channel data generating unit 14, a paging channel long PN code modulating unit 15, a speech input unit 16, a first speech process encoding unit 17, a first telephone communication channel long PN code modulating unit 18, a first short PN code modulating unit 19, a first carrier modulating unit 20, a first antenna unit 21, a second antenna unit 22, a reception decoding unit 23, an access channel data detecting unit 24, a preamble code detecting unit 27, a speech (voice) output unit 25, and a control unit 26. The first base station 310 transmits a plurality of paging channel signals, and signals from a plurality of telephones as electromagnetic waves, and also receives a plurality of access channels and a plurality of telephone communication signals sent from a plurality of mobile stations so as to control the respective mobile stations. Also, the first base station 310 transfers a telephone communication signal to a plurality of telephones.
FIG. 15 is a block diagram for showing an arrangement of the mobile station 301 indicated in FIG. 13. The mobile station 301 is arranged by employing a transmission/reception block 85 which includes: an access channel data generating unit 51, an access channel long PN code modulating unit 52, a first switching unit 53, a second short PN code modulating unit 54, a second carrier wave modulating unit 55, an antenna commonly-using unit 56, a third antenna unit 57, a microphone unit 58, a second speech process encoding unit 59, a preamble code generating unit 60, a second telephone communication channel long PN code modulating unit 61, a second carrier wave demodulating unit 62, a short PN code demodulating unit 63, a second switching unit 64, a Walsh “0” decoding unit 65, a pilot channel offset detecting unit 66, a Walsh “32” decoding unit 67, a sink channel data detecting unit 68, a paging channel Walsh code decoding unit 69, a paging channel long PN code decoding unit 70, a paging channel data detecting unit 71, a telephone communication channel Walsh code decoding unit 72, a telephone communication channel long PN code decoding unit 73, a speech process decoding unit 74, and a speaker unit 75. Also, this mobile station 301 is arranged by employing a logic control block 76 which contains a logic judging unit 77, a program memory unit 78, and a data memory unit 79. Further, this mobile station 301 is arranged by employing a peripheral block 86 which owns a key operation unit 80, a display unit 81, and a battery unit 82.
In the transmission/reception block 85, both a pilot channel signal and a sink channel signal, which are transmitted from a base station, are received so as to specify such a base station of a communication counter party, and in response to a mobile station calling signal in a paging channel and a calling signal sent from a mobile station in an access channel, a telephone communication line is set via the base station between a telephone set and the mobile station so that a telephone communication can be made. Also, while the logic control block 76 stores thereinto a control program, this logic control block 76 acquires information from the transmission/reception block 85, and outputs a necessary control signal to this transmission/reception block 85. The peripheral block 86 supplies electric power necessary for the above-described operations, and enters information required by a user, and also displays control conditions of the mobile station to the user.
Next, a description will now be made of various structural units which constitute the transmission/reception block 85, the logic control block 76, and the peripheral block 86. It should be understood that each of the respective units is not explained, but each of these blocks is described in descriptions of embodiment modes according to the present invention.
Subsequently, operations of the CdmaOne portable telephone system 300 will now be schematically explained with reference to FIG. 13 to FIG. 23. The mobile station 301 which constitutes the CDMA portable telephone system 300 indicated in FIG. 13 commences a telephone communication (telephone conversation) with respect to the first base station 310 of the first area 311 in which the mobile station 301 is located in accordance with the below-mentioned method.
First, signals transmitted from the first base station 310 to the mobile station 301 will now be explained. The pilot channel signal generating unit 11 indicated in FIG. 14 generates a pulse stream of “1” and “0” which are not modulated at a bit rate of 1.2288 Mbps, and then, this pulse stream is modulated based upon the Walsh “0” code by the Walsh code modulating unit 13. Also, the sink channel signal generating unit 14 generates sink channel data of 1.2 Kbps, and then this sink channel data is modulated based upon the Walsh “32” code by the Walsh code modulating unit 13. Also, the paging channel signal generating unit 19 generates a digital signal at bit rates of 2.4 Kbps to 9.6 Kbps for calling the mobile station 301. This digital signal is modulated based upon the long PN code by the paging channel long PN code modulating unit 15, and is furthermore modulated based upon the paging channel Walsh code by the Walsh code modulating unit 13.
A speech signal (voice signal) which is outputted from the first telephone 361 shown in FIG. 13 and sent via both the exchanging station 350 and the switching station 340 is supplied via the speech input unit 16 and the first speech process encoding unit 17 to the first telephone communication channel long PN code modulating unit 18, and then is modulated based upon the long PN code. This long-PN-code-modulated speech signal is modulated based on the telephone communication channel Walsh code by the telephone communication channel Walsh code modulating unit 13. In an actual case, there are plural portions of paging channel signals and portions of speech input signals, which are surrounded by a dot line of FIG. 14.
FIG. 16 is an explanatory diagram for explaining Walsh code modulating unit 13. There are 64 pieces of the Walsh codes in total. In a downstream line (namely, in a signal transfer line from base station to mobile station), the Walsh codes are employed in a channel identifications. A Walsh “0” code is used to identify a pilot channel; a Walsh “32” code is employed so as to identify a sink channel; and Walsh codes defined from a Walsh “1” code up to a Walsh “63” code except for the Walsh “32” code are used to identify a paging channel and a telephone communication channel.
FIG. 18 is an explanatory diagram for explaining a long PN code. In the downstream line, the long PN code is used so as to encrypt a signal. The pilot channel signal, the sink channel signal, a plurality of paging channel signals, and a plurality of speech signal, which are entered into the Walsh code modulating unit 13, are modulated based upon the Walsh codes corresponding thereto, respectively. These Walsh-code-modulated signals are synthesized with each other, and then the synthesized signal is inputted to the first short PN code modulating unit 19 so as to be modulated based on the short PN code.
FIG. 17 is an explanatory diagram for explaining the short PN code. In the downstream line, the short PN code is employed so as to identify a base station. Since the first base station 310, the second base station 320, and the third base station 330 utilize the previously explained Walsh codes in the channel identifications, the respective base stations use the same short PN codes in order to judge that a signal is transmitted from which base-station. As represented in FIG. 17, since these base stations use such short PN codes, the phases of which are shifted by 64 bits from each other, a mobile station may discriminate a base station from each other. This is called as an “offset”.
The synthesized signal which has been modulated based upon the short PN code by the first short PN code modulating unit 19 is entered into the first carrier wave modulating unit 20 so as to be carrier-modulated, and thereafter, this carrier-modulated signal is radiated as electromagnetic waves from the first antenna unit 21.
Next, operations of a mobile station will now be described. In the below-mentioned explanations, it should be understood that the mobile station 301 and the first base station 310 are merely referred to as a “mobile station” and a “base station”, and will be clearly defined as the “mobile station 301” and the “first base station 310” in a specific case, if necessary.
As shown in FIG. 20, operation stages are segmented into the below-mentioned four states, while these operation stages are defined by that after a power supply of a mobile station is turned on, the mobile station commences a telephone communication via a base station to a telephone subscriber, and continues the telephone communication until an end of the telephone communication:    Step S100: Initialization state,    step S200: Idle state,    Step S300: Access state, and    Step S400: Control on the traffic channels state.
FIG. 21 and FIG. 22 indicate further detailed operation steps of the respective states, and FIG. 23 shows operation routes of the respective operation steps.
First, in a step S1, a power supply of the mobile station is turned ON. When a user depresses a key corresponding to the turn-ON operation of the key operation unit 80 shown in FIG. 15, voltages of a battery unit 82 are applied to the respective units in response to an instruction of the logic control block 76. It is so assumed that the mobile station does not employ an analog type portable telephone system, but employs such a mobile telephone system which is exclusively designed for the CdmaOne system. In a step S2, the mobile station sets a wireless frequency number (radio frequency number) which has been stored in the own mobile station. Precisely speaking, both a transmission frequency and a reception frequency, which correspond to the wireless frequency number stored in the data memory unit 79 of the logic control block 76, are set to both the second carrier wave modulating unit 55 and the carrier wave demodulating unit 61.
In a step S3, the second switching unit 64 is switched to the side of the Walsh “0” decoding unit 65 in response to an instruction issued from the logic control block 76, and then, the process operation is advanced to a step S4. In this step S4, a pilot signal is supplied via the third antenna unit 57, the antenna commonly-used unit 56, and the carrier wave demodulating unit 62 to the short PN code demodulating unit 63 so as to be demodulated by this short PN code demodulating unit 63, and then, the output of this short PN code demodulating unit 63 is fed to the Walsh “0” decoding unit 65. In the Walsh “0” decoding unit 65, this output signal is furthermore decoded by employing the Walsh “0” code so as to seek a pilot channel having the highest signal strength, and then, the process operation is advanced to a step S5.
In the step S5, a pilot channel offset detecting unit 66 detects an offset of the short PN code, and then, the process operation is advanced to a step S6. It should also be noted that the offset number of the PN code could not be detected at this stage. Also, in the case that the offset of the short PN code cannot be detected but the reception of the pilot channel fails, the process operation is returned to the step S2. In this step S2, both a wireless transmission frequency and a wireless reception frequency, which correspond to another wireless frequency number stored in the data memory unit 79, are again set to the second carrier wave modulating unit 55 and the carrier wave demodulating unit 62, and then, the above-described operation is repeatedly carried out.
In a step S6, the second switching unit 64 is switched to the side of the Walsh “32” decoding unit 67 in response to an instruction issued from the logic control block 76 so as to receive a signal of a sink channel sent from the base station. In other words, as to the signal which has been demodulated by the carrier wave demodulating unit 62 and the short PN code demodulating unit 63, only the sink channel corresponding thereto is detected by the Walsh “32” decoding unit 67 from this signal, and then, the detected sink channel is supplied to the sink channel data detecting unit 68. In a step S7, in such a case that the data of the sink channel can be decoded in the above-described process operations, the process operation is advanced to a step S8. To the contrary, in the case that the data of the sink channel cannot be decoded, the process operation is returned to the step S3.
In the step S8, the sink channel data detecting unit 68 acquires the below-mentioned information, and then stores the acquired information into the data memory unit 79:
1) Protocol altered level of base station,
2) minimum protocol altered level supported by base station,
3) network identification code,
4) offset number of PN sequence of base station pilot channel,
5) state of long PN code,
6) system time, and
7) data rate of paging channel.
The mobile station grasps an offset number of a PN sequence of a pilot channel of a base station based upon the above-described information 4), and correctly recognizes that which base station is received.
In a step S9, a check is made as to whether or not the protocol level of the mobile station is higher than, or equal to the minimum level supported by the base station based upon the information acquired in the sink channel. If the check result becomes “No”, then the process operation is returned to the step S2. If the check result becomes “Yes”, then the process operation is advanced to a step S10. In the step S10, while both the information 5) “state of long PN code” and the information 6) “system time” acquired in the step S8 are employed, and also a content of the long PN code and timing information thereof transmitted from the base station are utilized, both a long PN code and timing thereof are set which are used in both the paging channel long PN code decoding unit 70 and the telephone communication channel long PN code decoding unit 73.
In a step S11, the second switching unit 63 is switched to the side of the paging channel Walsh code decoding unit 68 in response to an instruction issued from the logic control block 76, and then, data rate and the like are set from a code number of a paging channel based upon the information acquired in the sink channel in the step S8, and also, a paging channel signal transmitted from the base station is received. In other words, as to the signal which are demodulated by the carrier demodulating unit 61 and the short PN code decoding unit 62, only a paging channel corresponding to the paging channel Walsh code is detected, and is furthermore decoded by the paging channel long PN code decoding unit 69. That is to say, the data of the paging channel is decoded by employing the long PN code whose timing has been adjusted in the step S10, and then, the decoded data output is supplied to the paging channel data detecting unit 71. Then, this paging channel data detecting unit 71 acquires data related to a peripheral base station and a remaining base station, and then stores this data into the data memory unit 79. The process operation is advanced to a step S12.
The above-explained steps S1 to S11 correspond to the step S100 (namely, initialization state) shown in FIG. 20.
In a step S12, reception strengths of pilot channels of the respective base stations of the peripheral base station list and the remaining base station list are measured for a time duration until a telephone communication is commenced during waiting time period. Based upon the measurement results, the reception strengths of the pilot channels of the respective base stations are described in both the peripheral base station list and the remaining base station list so as to alter these lists, and then the process operation is advanced to a step S13. In this step S13, a check is made as to whether or not a reception signal strength of the present base station is lower than the minimum receivable signal length. Since the mobile station is moved even during the waiting time period, there is a certain possibility that the reception signal strength of the present base station becomes lower than the minimum receivable signal strength. When this reception signal strength becomes below than the minimum receivable signal strength, the process operation is advanced to a step S14. To the contrary, when the reception signal strength is not lower than the minimum receivable signal strength, the process operation is advanced to a step S16.
In the step S14, a check is made as to whether or not such a base station having a pilot channel whose reception level is higher than the minimum receivable signal strength is present in the peripheral base station list. When such a base station is not present in the peripheral base station list, the process operation is advanced to the step S3. On the other hand, when such a base station is present in the peripheral base station list, the process operation is advanced to a step S15. In this step S15, a selection is made of a paging channel of a base station which contains an offset number of a pilot channel whose reception strength become maximum (note that offset number of pilot channel will be simply referred to as “offset number” hereinafter) from the peripheral base station list, and then, the process operation is returned to the step S12.
In the case that the reception sensitivity is not lowered in the step S13, the process operation is advanced to a step S16. In the step S16, a check is made as to whether or not a telephone call is issued from the base station in the paging channel. When the telephone call is issued from the base station, the process operation is advanced to a step S18. On the other hand, in the case that the telephone call is not issued from the base station, the process operation is advanced to a step S17. In this step S17, a check is made as to whether or not a telephone call is issued from the mobile station to the base station. When the telephone call is issued, the process operation is advanced to a step S18. To the contrary, when the telephone call is not issued from the mobile station to the base station, the process operation is returned to the previous step S16.
The above-explained steps S12 to S17 correspond to the above-described step S200 (waiting state) shown in FIG. 20. In an actual case, there are other operations that the mobile station is identified and registered in the base station system in addition to the above-explained operations. However, since these operations have no direct relation to the explanations as to the operations of the present invention, these other operations are omitted.
In a step S18, there are two cases, namely in the case that the telephone call is issued from the base station in the step S16, and in the case that the telephone call is issued from the mobile station to the base station in the step S17, a communication is established to the base station by employing an access channel in any one of these two cases. Then, the process operation is advanced to a step S19. Precisely speaking, an access channel data generating unit 51 generates either data indicating that the mobile station receives a telephone call issued from the base station, or data representing that a telephone call is issued from the mobile station, and this generated data is modulated based upon the access channel long PN code by the access channel long PN code modulating unit 52, and then, this modulated data is supplied via the first switching unit 53 to the second short PN code modulating unit 54 so as to be modulated based upon the short PN code. This short-PN-code-modulated data is converted into a carrier wave by the second carrier wave modulating unit 55, and then is supplied via the antenna commonly-used unit 56 so as to be radiated as electromagnetic waves from the third antenna unit 57, so that a signal is transmitted to the base station. As indicated in FIG. 19, in an upstream line, the long PN code is used so as to discriminate the access channel from the telephone communication channel, and the short PN code is used in order to discriminate such that the mobile station is communicated with which base station.
Next, in a step S19, a check is made as to whether or not an instruction for starting a telephone communication is issued from the base station via the paging channel. When the instruction for starting the telephone communication is issued from the base station, the process operation is advanced to a step S20. On the other hand, in the step S20, a preamble code is transmitted to the base station via the telephone communication channel, while this preamble code is such a code for indicating that the mobile station receives the telephone communication starting signal of the base station. Then, the process operation is advanced to a step S21 in which the telephone communication is commenced.
Subsequently, the operations defined in the step S19, the step S20, and the step S21 will be explained in detail. In the step S18, the electromagnetic waves transmitted from the mobile station are received by the second antenna unit 22 of the base station, and then are detected via the reception decoding unit 23 by the access channel data detecting unit 24, and the access channel data detecting unit 24 grasps that the telephone call sent from the base station is detected by the mobile station, or grasps that the mobile station requests the base station to issue the telephone call, and then, informs this grasped content to the control unit 26. The control unit 26 informs this grasped content to the paging channel data generating unit 14. The paging channel data generating unit 14 radiates as electromagnetic waves from the first antenna unit 21, as previously explained, such an information for instructing the mobile station to start the telephone communication.
The electromagnetic waves radiated from the base station are received by the third antenna unit 57 of the mobile station. As previously explained, the paging channel data detecting unit 71 detects that the mobile station has been instructed from the mobile station to commence the telephone communication, and informs this information to the logic control block 76. The logic control block 76 informs this information to the preamble code generating unit 60, and at the same time, switches the first switching unit 53 to the side of the second telephone communication channel long PN code modulating unit 61, and also switches the second switching unit 64 to the side of the telephone communication channel Walsh code decoding unit 72. The preamble code of the preamble code generating unit 60 is modulated based upon the telephone communication channel long PN code by the second telephone communication channel long PN code modulating unit 61, as previously explained, and the modulated preamble code is radiated as the electromagnetic waves from the third antenna unit 57 toward the base station.
In this case, as a telephone communication channel long PN code used to discriminate a communication channel from each other, one of the long PN codes is employed. As indicated in FIG. 18, there are approximately 4.4 trillions of long PN codes, and since these 4.4 trillions of long PN codes may be separately allocated to the respective mobile stations, the base station need not designate a telephone communication channel, but merely instructs a mobile station to commence a telephone communication. Next, in the telephone communication operation defined in the step S21, the mobile station supplies the speech signal derived from the microphone unit 58 via the second speech process encoding unit 59 and the second telephone communication channel long PN code modulating unit 61, and as previously described, radiates the processed speech signal as the electromagnetic waves from the third antenna unit 57 toward the base station.
The electromagnetic waves radiated from the mobile station are received from the second antenna unit 22 of the base station, the speech signal transmitted from the mobile station is outputted via the reception decoding unit 23 by the speech output unit 25, and then, this speech signal is sent via the switching station 340 and the exchanging station 350 to the first telephone 361. On the other hand, the speech signal derived from the first telephone 361 is transferred via the exchanging station 350 and the switching station 340 to the speech input unit 16. As previously explained, this speech signal is radiated as electromagnetic waves from the first antenna unit 21 toward the mobile station. The electromagnetic waves are received by the third antenna unit 57, and as previously explained, are supplied via the antenna commonly-used unit 56, the second carrier wave demodulating unit 62, the short PN code demodulating unit 63, the second switching unit 64, the telephone communication channel Walsh code decoding unit 72, and the telephone communication channel long PN code decoding unit 73 to the speech process decoding unit 74, and then, the speech signal is transferred to the user of the mobile station by the speaker unit 75.
Finally, in a step S22, a check is made as to whether or not a telephone communication has been accomplished. When the telephone communication has not yet been completed, the process operation is returned to the step S21 in which the telephone communication is continued. On the other hand, when the telephone communication has been completed, the process operation is returned to the step S12.
The above-described steps S20 to S22 correspond to the step S400 (control on the traffic channels state) of FIG. 20. In an actual case, the signal confirmation operations are carried out two times in a reciprocation manner between the mobile station and the base station by employing the designated communication channel in a process step between the step S20 and the step S21. In the case that a telephone call is issued from the mobile station, a telephone number of a communication counter party is transmitted to the base station within the offset thereof. Since these operations are not related to the descriptions as to the operations of the present invention, explanations thereof are omitted.
It should be understood that while sequential operations related to the above-explained operations have been stored in the program memory unit 78, the sequential operations are sequentially read out therefrom in response to operations to the logic judging unit 77 for the execution purposes. Also, the display unit 81 may function as a means for notifying conditions to the user in correspondence with the respective operations, and the key operation unit 80 is used to enter a request of the user into the logic judging unit 77 in correspondence with the respective operations.